The invention relates to a method of providing a surface layer on a substrate, which surface layer brings about an inclined orientation of the molecules of a liquid crystalline layer in contact with the surface layer, at the interface between the surface layer and the liquid crystalline layer, and also relates to a liquid crystalline display cell which comprises at least one such substrate.
In the field of liquid crystalline display cells, there is a demand for substrates having a surface layer which induces molecules of a liquid crystalline layer in contact therewith to a strongly inclined orientation having an angle of inclination exceeding, for example, 3.degree.. For example, in the SBE-display cell, SBE standing for "Supertwisted Birefringen Effect", which cell comprises chiral nematic layers having angles of rotation which are larger than 90.degree., surface-induced angles of inclination larger than 5.degree. are required to preclude the occurrence of stripe instabilities in the liquid crystalline material applied.
To obtain such large angles of inclination, silicon oxide can be obliquely evaporated in a vacuum, onto the substrates. However, it is difficult and costly to apply this process for mass production. By way of alternative, synthetic resins, such as polyparaphenylene and some polyimides, which are subjected to complicated treatments, can be used. However, they have a poor reproducibility, and the mechanism bringing about the inclined orientation is not understood at all.